AIRCREW SAFETY & HEALTH

Cosmic Ionizing Radiation

What you need to know

Aircrew and passengers are exposed to cosmic ionizing radiation on every flight. Here you can learn more about cosmic ionizing radiation, how you can be exposed, exposure levels, and possible health effects.

What is cosmic ionizing radiation?

Cosmic ionizing radiationExternal (or cosmic radiation) is a form of ionizing radiation that comes from outer space. A very small amount of this radiation reaches the earth. At flight altitudes, passengers and crewmembers are exposed to higher levels of cosmic radiation.

Cosmic radiation exposures on aircraft include:

galactic cosmic radiation, which is always present

solar particle events, sometimes called “solar flares”

Are there any known health effects from cosmic ionizing radiation?

The World Health Organization (WHO) International Agency for Research on Cancer (IARC) says that ionizing radiation causes cancer in humans. Ionizing radiation is also known to cause reproductive problems. We are looking more specifically at whether cosmic ionizing radiation is linked to cancer and reproductive problems.

Most studies of radiation health effects have looked at groups with much higher radiation doses from different kinds of radiation (atomic bomb survivors; patients who received radiation therapy).

What is not known

We don’t know what causes most health problems that could be linked to radiation, including some forms of cancer and reproductive health issues like miscarriage and birth defects. If you are exposed to cosmic ionizing radiation and have these health problems, we can’t tell if it was caused by your work conditions or something else.

We don’t know what levels of cosmic radiation are safe for every person.

How much cosmic radiation are crewmembers exposed to?

The National Council on Radiation Protection and Measurements reported that aircrew have the largest average annual effective dose (3.07 mSv) of all US radiation-exposed workers. 1 Other estimates of annual aircrew cosmic radiation exposure range from 0.2 to 5 mSv per year.

What do guidelines or regulations say about cosmic radiation exposure levels in aircrew?

There are no official dose limits for aircrew in the United States, but there are national and international guidelines.

The International Commission on Radiological Protection (ICRP) considers aircrew to be exposed to cosmic radiation on their jobs. They recommend effective dose limits of 20 mSvExternal /year averaged over 5 years (that is, a total of 100 mSv in 5 years) for radiation workers and 1 mSv/year for the public. For pregnant radiation workers, the ICRP recommends a dose limit of 1 mSv throughout pregnancy. The National Council on Radiation Protection and Measurements has a 0.5 mSv recommended monthly radiation limit during pregnancy.

European Union member states require assessment of aircrew exposure when it is likely to be more than 1 mSv /year, and adjustment of work schedules so that no individual exceeds 6 mSv/year.

We are finding that some crewmembers may have exposure to cosmic radiation that is higher than what is recommended, and thus may be at greater risk for possible health effects.

What can crewmembers do to reduce exposure to cosmic radiation?

Bidding for a flight schedule to reduce cosmic radiation exposures is complicated, because reducing one exposure may increase another. Seniority, lifestyle, and personal issues also affect the ability to make these choices. Here are some actions you can consider:

Try to reduce your time working on very long flights, flights at high latitudes, or flights which fly over the poles. These are flight conditions or locations that tend to increase the amount of cosmic radiation the crewmembers are exposed to. You can calculate your usual cosmic radiation exposures. The FAA’s CARI program websiteExternal allows you to enter information to estimate your effective dose from galactic cosmic radiation (not solar particle events) for a flight.

If you are pregnant or planning a pregnancy, it is important to consider your work exposures, including cosmic radiation. If you are pregnant and aware of an ongoing solar particle event when you are scheduled to fly you may want to consider trip-trading or other rescheduling actions if possible.

For flight attendants, a NIOSH study found that exposure to 0.36 mSv or more of cosmic radiation in the first trimester may be linked to increased risk of miscarriage.

Also, although flying through a solar particle event doesn’t happen often, a NIOSH and NASA study found that a pregnant flight attendant who flies through a solar particle event can receive more radiation than is recommended during pregnancy by national and international agencies.

Regarding solar particle events:

NIOSH has estimated that pilots fly through about 6 solar particle events in an average 28-year career.

Avoiding exposure to solar particle events is difficult because they often happen with little warning. You can find out whether a solar particle event is currently active through these sources:

Reference

1 National Council on Radiation Protection and Measurements. Ionizing radiation exposure of the population of the United States. Report No. 160. Recommendations of the National Council on Radiation Protection and Measurements (NCRP). Bethesda, MD: National Council on Radiation Protection and Measurements, 2009.